The knee or knee joint is the hinge system at the juncture where the femur and the tibia are connected by a series of ligaments. It is one of the most mobile joints of the body. In normal movement, it can bend through a range of about 150 degrees and can experience limited twisting. The geometric shape of the femur and tibia as they fit together makes the knee stable. One ligament system holding these bones together is the knee capsule consisting of five ligaments forming a sleeve-like connection. Two additional ligaments that occupy the knee joint are called crossed or cruciate ligaments. Quadricep muscles on the thigh power extension of the leg and are connected to the quad tendon, which attaches to the kneecap. The kneecap is attached to the tibia by the kneecap tendon. Stability and mobility of the knee result from this relatively complex design. Almost any knee injury will restrict its normal range of motion. Five places are susceptible to injury. These are the ligaments, the cartilages, the muscles around the knees, the kneecap and the tendons. Possible injuries include sprained ligaments, tears of knee cartilages, fractures of the bone joints, damage to the kneecap and muscle tendons, and contusion and tears of the quad muscles.
Injury occurs as a result of overextension of the knee, or when a large external force is applied to the bent knee or when tremendous muscular force is applied to the knee by the performer, such as an athlete engaged in football, soccer, rugby, lacrosse or the like. When engaging in such activities, it is important to protect the knee against such injury. This is frequently done through the use of protective wraps, knee braces or like devices. Such devices commonly do not provide adequate support and protection to the knee or, if they do, tend to unduly inhibit normal motion of the knee whereby the full potential of the knee is not realized.